A decision support model for fertiliser recommendations for grazed pasture

Abstract

Decision support software for the evaluation of phosphorus (P) and sulphur (S) fertiliser strategies can assist farm consultants and their clients to determine pastoral agriculture fertiliser policies. The underlying dynamic model is based on the P and S cycles in the soil-plant-animal system, including fertiliser inputs and soil- and animalmediated losses. Initial soil fertility is estimated from the Olsen P and phosphate-extractable organic S soil tests, and recent fertiliser history. In the S sub-model organic S and elemental S pools are considered. Animal production responses to fertiliser are estimated from relationships between soil P and S status, fertiliser inputs, pasture relative yield and stocking rate. Maintenance and economically optimum fertiliser strategies can be automatically calculated or the user can enter their own scenarios. Alternative fertiliser policies can be evaluated in terms of nutrient budgets, soil P and S status, pasture and animal production, and economics. Keywords: decision support, economics, fertiliser, model, phosphorus, sulphur